While Williams has been a revelation in his first season back in the NRL since his infamous walkout in 2008, Thaiday believes the code-hopping Rooster needs to back up his outstanding season to be considered among future Immortals Greg Inglis, Cameron Smith and Billy Slater.

"I think he's a great athlete, but GI's an athlete too and he's been in our game for a number of years and proven himself over the number of years he's been playing," Thaiday told NRL.com.

"If Sonny decides to stay in our game, it'd be fantastic first of all for rugby league and that's when I'd start giving him the accolades.

"It's all about consistency. Not just one or two great seasons in our game, but continually proving yourself year after year, showing up at the top of your game. That's what deserves that kind of accolade."

The Broncos skipper does admit, however, that the premiership-winning second-rower has injected a level of confidence in a New Zealand team that not seen before.

"What he does is he brings a confidence and aura to the team," he said of the 28-year-old.

"He showed that at the Roosters this year with his leadership and his skill on the field. It really helped out a lot of the Roosters players, young and old.

"And he's doing the same with this Kiwi side. They've always been talented, but I think in the past they've lacked confidence and that's what Sonny brings."

"It's all about consistency. Not just one or two great seasons in our game, but continually proving yourself year after year."

The Kangaroos have received plenty of plaudits for a defence that hasn't conceded a try in over 320 minutes, but Thaiday reckons it'll be severely tested against an attack he rates better than the Kangaroos'.

"I personally have watched a couple of their games in the World Cup so far and the attack and skill level within their team is absolutely amazing," Thaiday said.

"If anything, I think they've got us in that department. Again, it's going to come back to our defence. We've got some great attacking players in our side in Johnathan Thurston, Cam Smith, Greg Inglis, and Billy [Slater] if he gets the chance to play.

"To be honest, it's a 50/50 game. I couldn't tell you who's more in form or not, but at the end of the day, this is the World Cup final a lot of people wanted to see."

The World Cup final will be particularly meaningful for the 28-year-old Thaiday, who missed out on the decider in 2008. Sunday's game against New Zealand will be his 19th Test, and he hinted this World Cup could be his last.

"I remember 2008 and I had missed out through injury, which was pretty disappointing for myself," he said.

"I think we played Melbourne in the semi-final and I hurt my ankle and was out for six weeks. The hardest thing for me too was that it was in Australia so it was on the telly and I was watching every game.

"The final was in Brisbane as well. To have it in my home town of Brisbane, to have the final there, to see the boys and the heartbreak... I'm happy I'm in the position I am now and am looking forward to the chance to win the World Cup because these things don't come around often.

"And who knows, by the time the next one comes around, form-wise I might not be in the side, or age-wise I might not be in contention. I'll be making sure I do everything I can and do my job for the team."